We analyse the problem of the choice of the market variable in a model where firms activate R&D investments for process innovation. We establish that (i) firms always choose the Cournot behaviour; and (ii) there exists a set of the relevant parameters where a benevolent social planner prefers quantity setting to price setting. This happens when the marginal cost of R&D activities is relatively low while technological externalities are relatively high. In this situation, the conflict between social and private preferences over the type of market behaviour disappears.